drm/ttm: Remove unnecessary '0' values from ret

The variable ret is assigned in the judgment branch statement, he does
not need to initialize the assignment.
Signed-off-by: Li zeming <zeming@nfschina.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220907032934.4490-1-zeming@nfschina.comReviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

include/drm/ttm/ttm_bo_driver.h

@@ -106,7 +106,7 @@ static inline int ttm_bo_reserve(struct ttm_buffer_object *bo,
 				 bool interruptible, bool no_wait,
 				 struct ww_acquire_ctx *ticket)
 {
-	int ret = 0;
+	int ret;
 
 	if (no_wait) {
 		bool success;